Disconnected Maf/ No change

Hi I have black smoke coming out the back of my car when I drive. My first port of call was to see if the MAF was working so I switched the engine on (I know I should not do this but the car had no previous error codes) and disconnected the MAF while it was idling. The funny thing was that there was no difference in idling, engine noise ot anything else. I did not take it for a drive with the MAF disconnected. Can anyone advise me what to do if the MAF is ok or not and if it can be the cause of the black smoke and also 35 mpg im getting at the moment. Car is a 2002 A4 TDi SE 130. Also If I can do need a maf where can I get one from?